Closed Loop Control of Z-Source Inverters Involving Composite Partial Pole-Zero Cancellation Strategy

Z-Source Inverters (ZSIs) exhibit both buck and boost capabilities which make it suitable for many applications such as in Industrial drives, Photovoltaic, Uninterrupted power supply etc. The transient modelling of ZSI results a Non-Minimum Phase transfer function having a Right-Half-Plane Zero. This Non-Minimum Phase transfer function causes an initial capacitor voltage undershoot which is highly undesirable for sensitive operations with ZSIs. Further this Non-Minimum Phase function and undershoot leads to bandwidth limitation, high inductor inrush currents, Electromagnetic Interference, High inductor current ripple, increased voltage and current stress in the switches etc. This paper presents an idea to minimise the initial undershoot upto a tolerable limit by cancelling RHP Zero using partial pole (fractional order) insertion upto an arbitrary degree. Here classical PID control is used in simulations and the results are found to be verified and promising.